1. Field of the Invention
The invention relates to a method of producing molds and mold sections for foundry purposes, particularly for the production of cores composed of at least two core sections which are fixed to one another, with the individual core sections being separately molded in a core box composed of at least two box parts.
The term "core" in the sense of this application is understood to mean, on the one hand, composite mold sections which are placed into a casting mold and solve problems with respect to cavities, undercuts and similar concerns in casting mold design, i.e. foundry cores in the conventional sense. On the other hand, the term includes, within the scope of the present invention, also the casting mold itself which is composed of a plurality of sections made of the same molding material and according to the same method as foundry cores. Depending on the shape of the casting to be produced, the inner walls and/or also the outer walls of the casting may be delimited by the assembled "core sections".
2. Discussion of the Prior Art
In the past, composite cores were produced in that the individual core sections were molded, removed from the core mold and intermediately stored, whereupon they were joined by hand. The firm connection between the individual core sections was here produced either by screwing or a friction lock in the form of conical pins and conical recesses disposed at the core sections, with an appropriate compression pressure having to be applied. The thus firmly joined, complete core was then placed onto a conveying means, for example a pallet and, for certain cases of use, was blackened by immersion in an appropriate device, in which case the excess immersion fluid was centrifuged away. This method is very time-consuming and additionally has the drawback that the depositing and picking up of individual core sections between the individual manufacturing stages subjects the core sections to unnecessary stresses which lead to breakouts or also to abrasion which results in deviations from set dimensions, displacement of the core sections with respect to one another, crevices or the like. As a consequence, the castings produced with such cores require subsequent work at considerable expenditures for labor, with displacement or splitting, in particular, producing burrs at the casting which must be removed at least in those regions of the casting which are not subjected to subsequent mechanical processing phases. For complicated casting molds, such as, for example, engine blocks for motor-vehicle engines, some of these regions are very difficult to reach so that the removal of casting burrs is very labor intensive.
DE-A Nos. 1,253,415 and DE-A1 3,200,193 disclose apparatus in which two mold sections are molded in one core mold box and the subsequent joining of the two core halves is effected by a relative movement of the two core box halves still in the core molding machine. The core box halves here remain firmly connected with one another so that guiding and centering of the core sections to be joined is effected by way of the core box halves themselves. The drawback of these prior art methods is that only two-part cores and thus practically only foundry cores in the conventional sense can be produced. Complicated, multi-part casting molds cannot be produced in this manner.